Reland: Fix setComposingText with empty text when newCursorPosition != 1

content/renderer/render_widget.cc

Index: content/renderer/render_widget.cc
diff --git a/content/renderer/render_widget.cc b/content/renderer/render_widget.cc
index cc25047179fdb7ca43ece0e0e0d8497929d995aa..cbe00003273845a2c5a1bb729a57340a52f4d745 100644
--- a/content/renderer/render_widget.cc
+++ b/content/renderer/render_widget.cc
@@ -1508,6 +1508,29 @@ WebRect RenderWidget::windowResizerRect() {
   return resizer_rect_;
 }
 
+void RenderWidget::adjustSelectionForBoundary(int& selectionStart,

[yosin_UTC9, 2016/06/15 05:34:41]

Please follow Chromimum coding style:
http://dev.chromium.org/developers/coding-style
Roughly similar to Google C++ coding style.

Major thing is you should use pointer for output parameter rather than
reference.
How about using |std::pair<int, int>>|?

+                                              int& selectionEnd,
+                                              const int textLength) const {
+  int compositionLength =
+        text_input_info_.compositionEnd - text_input_info_.compositionStart;
+  int beforeCompositionLength;
+  if (compositionLength != 0)
+      beforeCompositionLength = text_input_info_.compositionStart;
+  else
+      beforeCompositionLength = text_input_info_.selectionStart;
+  int afterCompositionLength =
+      static_cast<int>(text_input_info_.value.length()) - compositionLength -
+      beforeCompositionLength;
+
+  // In case of exceeding the left boundary.
+  selectionStart = std::max(selectionStart, -beforeCompositionLength);
+  selectionEnd = std::max(selectionEnd, selectionStart);
+
+  // In case of exceeding the right boundary.
+  selectionEnd = std::min(selectionEnd, textLength + afterCompositionLength);
+  selectionStart = std::min(selectionStart, selectionEnd);
+}
+
 void RenderWidget::OnImeSetComposition(
     const base::string16& text,
     const std::vector<WebCompositionUnderline>& underlines,
@@ -1516,6 +1539,9 @@ void RenderWidget::OnImeSetComposition(
   if (!ShouldHandleImeEvent())
     return;
   ImeEventGuard guard(this);
+
+  adjustSelectionForBoundary(selection_start, selection_end, text.length());
+
   if (!webwidget_->setComposition(
       text, WebVector<WebCompositionUnderline>(underlines),
       selection_start, selection_end)) {